This invention relates in general to apparatus for heating water with smoke from a furnace, and more particularly to apparatus for recovering some of the energy from the smoke from a furnace wherein the smoke passes through heat exchanging means of a double concentric pipe configuration within the tank.
Various types of devices for recovering some of the heat or energy from smoke, and heating water therewith, are known to the prior art. Some prior art efforts have concentrated on recovering energy in and from the chimney. Such efforts have not proven successful for a number of reasons. Oftentimes the apparatus inserted into the chimney restricts a major portion thereof such that normal convection of the smoke up the chimney is interfered with. Adapting the chimney for recovery of energy therefrom is usually only practicable when the building, including the chimney, are being constructed. Furthermore, once the apparatus is installed in the chimney, any repair of the apparatus, as may be needed, becomes quite difficult and costly because of the difficulty in gaining access to the apparatus within the chimney.
Other prior art efforts have concentrated upon placing coils or jackets into or around the smoke flue to heat water contained within the coil or jacket. These prior art efforts have also been generally unsuccessful. The volume of water contained by such coils or jackets has generally been insufficient to either supply heated water in desired volume or to achieve efficient transfer of energy between the smoke and the water.
A further problem characteristic of all the prior art is that the coils, jackets and the like, which are used in the smoke flue or chimney experience moisture condensation on the surfaces thereof when exposed to the smoke. This moisture condensation results from the coils, water jackets and the like having a considerable temperature differential as compared to the temperature of the smoke. Any moisture condensation of the apparatus within the smoke flue or chimney immediately attracts soot and ash generated by the smoke source which results in the apparatus becoming coated with soot and ash. The soot and ash accummulations on the apparatus may become great enough to hamper normal convection of smoke within the flue or chimney. In any event, the heat exchanging efficiency between the apparatus and the smoke quickly deteriorates as soot and ash accummulate on the apparatus.